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Child and Family Studies
ENSC 1005
Heather Kaye

Monday January 21, 2013 Water - Covers 70% of Earth’s surface – 97% is saltwater, 3% is freshwater (most of which is locked up in glaciers, ice caps or inaccessible groundwater; a very small amount is easily available to us) - Most available freshwater continuously recycled (See FIG 15.3) Properties – water is unique and has important properties because of its attractive forces between molecules 1) Cohesiveness & adhesion – strong attractive forces hold molecules together and cause it to adhere/coat solids 2) High boiling point/low freezing/melting point – water remains a liquid over a wide temperature range (0 degrees – 100 degrees); water absorbs heat and releases heat as it changes state 3) High specific heat capacity – stores large amount of heat so changes temperature slowly 4) Universal solvent – dissolves many compounds 5) Filters out sun’s UV wavelengths – protects some aquatic organisms 6) Expands when it freezes – less dense Functions - Shape Earth’s surface - Regulate climate - Dilute/degrade wastes - Habitat for organisms Supplies - Surface water - Groundwater (natural recharge aquifers, fossil aquifers) Demands - Irrigation for crops – biggest user of water - Energy production (oil, gas & power plant cooling) - Industrial processing Problems 1) Freshwater shortage – demand exceeds supply 2) Too much – increase in deforestation (urbanization) leads to increase in flooding Managing Resources 1) Increase supply (build dams and reservoirs, tapping groundwater) 2) Improve efficiency Supplying More Water 1) - Construction of dams and reservoirs (See FIG 15.13) - Water released as needed for hydroelectric power, irrigation, control flooding, recreational purposes - Loss of land and habitat 2) - Tapping groundwater (See FIG. 15.16, 15.10) - Aquifer depletion, subsidence, intrusion of saltwater into aquifers as well as pollutants - Control population growth; develop crops that require less water 3) – Desalination - Removing salt from ocean waters by distillation/reverse osmosis - Expensive use of electricity Using Water More Efficiently 1) Conserve water 2) Reduce irrigation losses (See FIG 15.21) 3) Wasting less water in industry 4) Wasting less water in homes and businesses (See FIG 15.22) Water Pollution Categories of Water Pollutants (See FIG 22.1) 1) Infectious Agents – disease-causing organisms (pathogens) 2) Oxygen-Demanding Wastes – organic wastes that can be decomposed by aerobic (O2 requiring) bacteria - BOD (biological oxygen demand) is the amount of dO2 to breakdown organic ma
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